The electronics industry is continuously striving to create electronic devices which are smaller, cheaper, and provide higher resolution performance. As such, it has become necessary to develop new photo-imageable compositions and processes for photo-patterning which accomplish these goals.
Photo-patterning technologies offer uniform finer lines and space resolution when compared to traditional screen-printing methods. A photo-patterning method, such as DuPont's FODEL® photo-imageable thick film pastes, utilizes a photo-imageable organic medium as found in U.S. Pat. Nos. 4,912,019; 4,925,771, 5,049,480, 5,851,732 and 6,075,319 whereby the substrate is first completely covered (printed, sprayed, coated or laminated) with the photo-imageable thick film composition and dried, if necessary. An image of the pattern is generated by exposure of the photo-imageable thick film composition with actinic radiation through a photo-mask bearing a pattern. The exposed substrate is then developed. The unexposed portion of the pattern is washed away leaving the photo-imaged thick film composition on the substrate that is then fired to remove organic materials and sinter inorganic materials. Such a photo-patterning method demonstrates thick film line resolution of about 30 microns or larger depending on the substrate smoothness, inorganic particle size distribution, exposure and development variables. It has been proven that such a technique is useful in the manufacture of flat panel displays, such as plasma display panels.
However, the photo-imageable thick film compositions and tape compositions of the prior art typically do not incorporate photo-reactive groups in the polymer resin itself (As is the case in U.S. Pat. Nos. 4,912,019; 4,925,771, 5,049,480, 5,851,732 and 6,075,319).
U.S. Pat. No. 6,342,322 to Kakinuma et al. and JP3218767B2 to Masagi disclosed photosensitive compositions comprising specific photosensitive resins, a diluent, a photosensitive initiator, inorganic powder, and a stabilize.
Masagi discloses a photosensitive composition having an acrylic copolymer as the photosensitive resin. This again demonstrates the use of a photosensitive resin in a photosensitive composition.
The present inventors desired to provide a more economic and environmentally friendly composition(s), method of photo-patterning, and method of forming an electrode. By creating a novel composition(s) and processes, which do not require pre-formation of a photosensitive polymer in a separate process, the inventors accomplished this goal.
This invention discloses novel thick film pastes and tape compositions that generate in processing photosensitive polymers which may be photo-patterned. Unlike the prior art, the thick film paste composition of the present invention do not contain a photosensitive resin, but generate photosensitive resins during processing to form the desired photo-imaged pattern.